Parts manufactured from fiber reinforced plastic (FRP) parts are frequently bonded to other FRP parts or metal parts through the use of polyurethane adhesives. It has been common practice to treat the surfaces to be bonded by sanding and/or by wiping with a primer solution. Typically this primer solution consists of a diisocyanate in methylene chloride (2 percent PAPI). It has been shown by surface spectroscopy that methylene chloride removes a layer of low molecular weight materials, mostly hydrocarbons, from the FRP surface. The diisocyanate can then react with the FRP surface and the polyurethane adhesive.
Without the use of such a treatment, long term adhesion strength is reduced and at times even initial adhesion strength is not adequate. However, methylene chloride and free isocyanates are not desirable materials to use in manufacturing. On the other hand sanding is labor-intensive and can cause environmental (dust) problems.
In the manufacture of semiconductor products, where very clean metal and semiconductor surfaces are required, an UV/Ozone treatment is used for cleaning (C. E. Bryson et al, Surface Contamination, Genesis, Detection and Control, Vol. 1, K. L. Mittal Ed., Plenum 1979).
It is known that while exposure to short wavelength UV light or exposure to ozone alone will have some effect, the simultaneous exposure to UV light and ozone is many times more effective than either factor alone (John R. Vig, "UV/Ozone Cleaning of Surfaces: A Review," ibid).
The surface treatment of high density polyethylene and low density polyethylene with ozone and separately with a UV lamp oxidizes the surface to produce carboxyl groups (James Peeling et al, J. Polymer Sci. Poly. Chem. 21, 2047, 1983). See, also, Kirk-Othmer, "Encyclopedia of Chemical Technology,"Third Edition, Volume 16, John Wiley & Sons, New York, 1981, pages 689-690 regarding UV irradiation of air or oxygen to produce ozone. The wear and static properties of vinyl chloride polymer based gramophone records are improved by treatment of their surfaces with UV at 200 nm in an atmosphere of oxygen at a pressure of at least 15 Torr (U.S. Pat. No. 4,307,045). 1 Tor=1 mm of Hg. nm=nanometer.
Polyethylene terephthalate films can be photoetched with UV radiation having wavelengths less than 220 nm (U.S. Pat. No. 4,417,948).
Polyimides can be photoetched using lasers or low pressure Hg lamps (UV radiation) (European Patent Application Publ. No. 0 108 189 A2).
An aspect of this invention is to avoid the difficulties alluded to above and to provide a new method for adhering together FRP parts.
An aspect is to provide a novel FRP laminate.
These and other aspects and advantages of the present invention will become more apparent to those skilled in the art from the following detailed description and working examples.